Transflective type LCD and method for manufacturing the same

ABSTRACT

In a transflective type LCD provided with a transparent region and a reflection region in each pixel, when an irregular film  11  is formed on an active matrix substrate  12  to form irregularities of a reflection electrode film  6 , the irregular film  11  is specifically formed to almost the same film thickness in both the transparent region and the reflection region to provide substantially the same inter-substrate gap in these two regions so that they may have almost the same V-T characteristics and also the reflection electrode film  6  made of Al/Mo is formed so as to overlap with a transmission electrode film  5  made of ITO all around an outer periphery of the transmission electrode film  5  by a width of at least 2 μm, thus suppressing electric erosion from occurring between the ITO and Al substances at the edge of the transmission electrode film  5.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/205,365, filed Jul. 26, 2002 now U.S. Pat. No. 6,853,421.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a Liquid Crystal Display (LCD) andmethod for manufacturing the same and, more particularly to, atransflective active-matrix type LCD having a transmission region and areflection region in its pixel and method for manufacturing the same.

2. Description of the Related Art

Because of its features of a small and thin geometry and low powerconsumption, an LCD has been put to practical use in a variety ofapplications such as an OA apparatus and a portable apparatus. The LCDsare classified in a transmission type and a reflection type, the LCD ofthe transmission type of which has no function to emit light for itselfunlike a CRT or an EL display and so is provided with a back-lightsource separately so that display may be controlled bytransmitting/blocking the back-light of liquid crystal thereof.

Although the transmission type LCD can use back-light to obtain brightdisplay independently of the surrounding environments, a back-lightsource thereof typically has large power consumption of substantially ahalf of the total consumption thereof, thus contributing to an increasein the overall power consumption. If the LCD is driven by a battery inparticular, its operating time is decreased, while if a large sizedbattery is mounted thereto on the other hand, its total weight isincreased, thus preventing improvements in size and weight thereof.

To solve this problem owing to large power consumption of the back-lightsource, a reflection type LCD is suggested which utilizes surroundinglight for display. The reflection type LCD employs a reflecting plate inplace of the back-light source to transmit/block the surrounding lightreflected by the reflecting plate in order to control display, so thatit need not have a back-light source, to thereby reduce its powerconsumption, size, and weight; at the same time, however, it is largelydeteriorated in visibility problematically if the surroundings are dark.

Although the transmission type and reflection type LCDs have theseadvantages and disadvantages of their own, a back-light source isrequired in order to obtain stable display but inevitably increasespower consumption of the LCDs if only it is used as the light sourcethereof. To solve this problem, for example, Japanese Patent Application(KOKOKU) Laid-Open No. Hei 11-101992 discloses a transflective type LCDwhich can suppress power consumption of its back-light source and securevisibility independently of the surrounding environments, in which atransmission region and reflection region are provided in each pixelthereof to enable providing transmission mode display and reflectionmode display on a single liquid crystal panel.

A conventional transflective type LCD is described as follows withreference to FIG. 18. FIG. 18 is a cross sectional view of conventionaltransflective type LCD.

As shown in FIG. 18, the conventional transflective type LCD comprisesan active matrix substrate 12 on which a switching element such as aThin Film Transistor (hereinafter abbreviated as TFT) 3 is formed, anopposing substrate 16 on which a color filter, a black matrix, etc. areformed, a liquid crystal layer 17 sandwiched by these substrates, and aback-light source 18 arranged below the active matrix substrate 12.

On the active matrix substrate 12 is provided with a gate line and adata line and, near an intersection thereof, a TFT 3, in such aconfiguration that a drain electrode 2 a and a source electrode 2 b ofthe TFT3 are connected to the data line and a pixel electroderespectively. Each pixel is divided into a transmission region whichtransmits back-light and a reflection region which reflects surroundinglight in such a construction that the transmission region has atransparent electrode film 5 formed on a passivation film 10 and thereflection region has a reflection electrode film 6 made of metal on anirregular film 11 made of an organic substance.

In this construction of the transflective type LCD, in the transmissionregion, back-light radiated from a back side of the active matrixsubstrate 12 passes through the liquid crystal layer 17 and is emittedfrom the opposing substrate 16, while in the reflection region,surrounding light injected through the opposing substrate 16 once entersthe liquid crystal layer 17 and is reflected by the reflection electrodefilm 6 and passes back through the liquid crystal layer 17 and then isemitted from the opposing substrate, so that there occurs a differencein optical path length between the transmission region and thereflection region.

To guard against this, conventionally, a polarization state of theemitted light has been adjusted so as to equalize the optical pathlengths of the liquid crystal layer 17 in these two regions to eachother by forming the organic irregular film 11 in the reflection regionthicker than that in the other so that the gap of the liquid crystallayer 17 in the reflection region may be substantially a half of that inthe transmission region.

Generally, the gradation-luminance characteristics of the liquid crystalpanels need to be the same in the transmission region and the reflectionregions so that an image impression in the transmission mode may matchthat in the reflection mode. For this purpose, the voltage-luminancecharacteristics (V-T) of the panel in the transmission mode may agreewith those in the reflection mode.

In the above-mentioned conventional transflective type LCD, however, agap of the liquid crystal layer 17 is different in the reflection regionand the transmission region, that is, the gap with respect to theelectrode is different on the side of the active matrix substrate 12 andon the side of the opposing substrate 16, so that the strength of anelectric field applied on the liquid crystal cannot be equal in thevarious regions, to result in a change in luminance in these regions,thus problematically deteriorating the display quality.

SUMMARY OF THE INVENTION

In view of the above, it is a main object of the present invention toprovide a transflective type LCD and method for manufacturing the samewhich can match the voltage-luminance characteristics of the panel inthe transmission mode with those in the reflection mode and also whichcan suppress occurrence of a pixel defect caused by a reflectionelectrode film or a transparent electrode film.

In order to achieve above mentioned object, a transflective type LCDaccording to present invention comprising: a plurality of scanning linesand a plurality of signal lines which are substantially perpendicular toeach other and a switching element arranged near each of intersectionsbetween said scanning lines and said signal lines on a first substrate;a transmission region in which a transparent electrode film is formedand a reflection region in which a reflection electrode film is formedwhich regions are provided in each pixel surrounded by said scanninglines and said signal lines; and liquid crystal sandwiched at a gapbetween said first substrate and a second substrate which is arrangedopposite to said first substrate, wherein an organic film below saidreflection electrode film which underlies irregularities of saidreflection electrode film is formed also below said transparentelectrode film as shaped irregular with almost the same film thicknessso that said gap may be substantially equal both in said transmissionregion and said reflection region.

Moreover, in the transflective type LCD, wherein said reflectionelectrode film is formed on the side of the pixel where said switchingelement is arranged, so that a terminal of said switching element isconnected with said reflection electrode film via a through hole formedin said organic film and said transparent electrode film is connectedwith said reflection electrode film in an overlap region thereof.

Moreover, in the transflective type LCD, wherein such a portion (G-Dconversion portion) as to lead out said signal line by means of a gatelayer is connected with either one of said reflection electrode film andsaid transparent electrode film in a circumference of said firstsubstrate.

Moreover, in the transflective type LCD, wherein: on such a side of eachof said first substrate and said second substrate as to be opposite tothe sides thereof which sandwich said liquid crystal therebetween, a λ/4plates and a polarizing plates are arranged in this order from the sideof said substrate; said polarizing plate on an outer side of said firstsubstrate and said polarizing plate on an outer side of said secondsubstrate are arranged so that polarization axes thereof may beperpendicular to each other; and a twist angle of said liquid crystal isset at 72 degree.

Moreover, a method for manufacturing a transflective type LCD accordingto the present invention, in said transflective type LCD having a firstsubstrate provided thereon with a plurality of scanning lines and aplurality of signal lines which are substantially perpendicular to eachother and a switching element arranged near each of intersectionsbetween said scanning lines and said signal lines, forming a reflectionregion having a reflection electrode film and a transmission regionhaving a transparent electrode film in each pixel surrounded by saidscanning lines and said signal lines and the liquid crystal issandwiched at a gap between said first substrate and a second substratewhich is arranged opposite to said first substrate, the methodcomprising the steps of: when forming an organic film havingirregularities thereon is formed below said reflection electrode filmand said transparent electrode film to substantially the same filmthickness, forming a half-tone mask having a transmission portion, ashielding portion and a transflective portion in said pixel portion; andforming said irregularities and a portion where said organic film iscompletely removed using the said mask at a same time.

Moreover, in a method for manufacturing a transflective type LCDaccording to the present invention, in said transflective type LCDhaving a first substrate provided thereon with a plurality of scanninglines and a plurality of signal lines which are substantiallyperpendicular to each other and a switching element arranged near eachof intersections between said scanning lines and said signal lines,forming a reflection region having a reflection electrode film and atransmission region having a transparent electrode film in each pixelsurrounded by said scanning lines and said signal lines and the liquidcrystal is sandwiched at a gap between said first substrate and a secondsubstrate which is arranged opposite to said first substrate, the methodcomprising the steps of: when forming an organic film havingirregularities thereon is formed below said reflection electrode filmand said transparent electrode film to substantially the same filmthickness, forming a first organic film as scattered in dot; performingpredetermined heat treatment to form protrusions; and coveringmoderately by a second organic film to form said predeterminedirregularities.

Moreover, in the method of present invention, wherein when forming awindow portion for said transmission portion by removing a part of saidreflection electrode film, etching said reflection electrode film so asto overlap with said transmission electrode film by a predeterminedwidth around an overall periphery of said window portion as viewed froma direction of a normal line of said substrate, and it is preferablysaid etching is performed so that said width for overlapping may beabout 2 μm.

Moreover, in the method of present invention, wherein said reflectionelectrode film is of a two-layer construction consisting of a barriermetal film and a reflection metal film, each of which is formed to afilm thickness at least 100 nm, more preferably about 200 nm or more.

Moreover, in the method of present invention, wherein when at least oneof said barrier metal film and said reflection metal film is formed, themetal film is once formed to a predetermined film thickness, then washedby an alkali solution, and then formed again to a desired filmthickness.

Moreover, in the method of present invention, wherein Mo is used as amaterial of said barrier metal film and Al is used as a material of saidreflection metal film.

Moreover, in the method of present invention, wherein at the washingstep by use of UV ray prior to formation of said transparent electrodefilm, an application quantity of the UV ray is limited down to a valueless than 100 mJ.

Moreover, a method for manufacturing a transflective type active matrixsubstrate according to present invention, said transflective type activematrix substrate being provided with a plurality of scanning lines and aplurality of signal lines which are substantially perpendicular to eachother and a switching element arranged near each of intersectionsbetween said scanning lines and said signal lines in such aconfiguration that a reflection region having a reflection electrodefilm and a transmission region having a transparent electrode film areformed in each pixel surrounded by said scanning lines and said signallines, the method comprising at least the steps of: depositing apassivation film on a substrate on which said scanning lines, saidsignal lines, and said switching elements are formed and then forming afirst contact hole in a portion (G-D conversion portion) which, isprovided around said substrate to lead out said signal line by means ofa gate layer; filling said first contact hole with a predeterminedconductive material to connect said G-D conversion portion therewith;depositing an organic film to almost the same film thickness both insaid transmission region and said reflection region, then formingirregularities on the surface and also removing said organic film on aterminal of said switching element to form a second contact hole;forming a transparent electrode film on said organic film in saidtransmission region; and forming a reflection electrode film in such amanner that said reflection electrode film may overlap with saidtransparent electrode film around an overall periphery thereof by apredetermined width to interconnect said terminal and said reflectionelectrode film through said second contact hole.

Moreover, a method for manufacturing a transflective type active matrixsubstrate, said transflective type active matrix substrate beingprovided with a plurality of scanning lines and a plurality of signallines which are substantially perpendicular to each other and aswitching element arranged near each of intersections between saidscanning lines and said signal lines in such a configuration that areflection region having a reflection electrode film and a transmissionregion having a transparent electrode film are formed in each pixelsurrounded by said scanning line and said signal line, the methodcomprising at least the steps of: depositing a passivation film on asubstrate on which said scanning lines, said signal lines, and saidswitching elements are formed and then forming a first contact hole in aportion (G-D conversion portion) which is provided around said substrateto lead out said signal line by means of a gate layer; depositing anorganic film to almost the same film thickness both in said transmissionregion and said reflection region, then forming irregularities on thesurface and also removing said organic film on a terminal of saidswitching element to form a second contact hole; forming a transparentelectrode film on said organic film in said transmission region and alsofilling said first contact hole with said transparent electrode film toconnect said G-D conversion portion therewith; and forming a reflectionelectrode film in such a manner that said reflection electrode film mayoverlap with said transparent electrode film around an overall peripherythereof by a predetermined width to interconnect said terminal and saidreflection electrode film through said second contact hole.

In an configuration according to the present invention, the gap of theliquid crystal layer can be substantially equal in the transmissionregion and the reflection region so that the V-T characteristics in thetransmission mode may agree with those in the reflection mode; also, byimproving an adhesiveness of the transparent electrode film to protectthe edge of the transparent electrode film securely, it is possible tosuppress a defect from occurring owing to a developer during the PR(photo resist) step for forming the reflection electrode film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view for showing a configuration of a transflectivetype LCD related to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view for showing the configuration of thetransflective type LCD related to the first embodiment of the presentinvention;

FIG. 3 is an illustration for showing a polarization state of incidentlight and reflected light of the transflective type LCD related to thefirst embodiment of the present invention;

FIG. 4 is a graph for showing a relationship between a twist angle and agap in a transmission region and a reflection region of liquid crystal;

FIG. 5 are graphs for showing V-T characteristics at predetermined twistangle as well as the gap in the transmission and reflection regions ofthe liquid crystal;

FIG. 6 is a plan view for showing a configuration of the transflectivetype LCD related to a second embodiment of the present invention;

FIG. 7 is a cross-sectional view for showing the configuration of thetransflective type LCD related to the second embodiment of the presentinvention;

FIG. 8 are cross-sectional views for showing a problem of a conventionaltransflective type LCD;

FIG. 9 is a cross-sectional view for showing an effect of thetransflective type LCD related to a third embodiment of the presentinvention;

FIG. 10 is a microscopic picture for showing abnormal display of theconventional transflective type LCD;

FIG. 11 are cross-sectional flow diagrams for showing a transflectivetype LCD manufacturing method related to a fourth embodiment of thepresent invention;

FIG. 12 are cross-sectional flow diagrams for showing the transflectivetype LCD manufacturing method related to the fourth embodiment of thepresent invention;

FIG. 13 are the cross-sectional flow diagrams for showing thetransflective type LCD manufacturing method related to the fourthembodiment of the present invention;

FIG. 14 are cross-sectional flow diagrams for showing the transflectivetype LCD manufacturing method related to a fifth embodiment of thepresent invention;

FIG. 15 are the cross-sectional flow diagrams for showing thetransflective type LCD manufacturing method related to a fifthembodiment of the present invention;

FIG. 16 is a plan view for showing a construction of the transflectivetype LCD related to a prior application of the present inventor;

FIG. 17 is a cross-sectional view for showing the construction of thetransflective type LCD related to the prior application of the presentinventor; and

FIG. 18 is a cross-sectional view for showing a construction of theconventional transflective type LCD.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following will describe preferred embodiments of a transflectivetype LCD related to the present invention with reference to drawings.

As mentioned above, generally in a transflective type LCD, thegradation-luminance characteristics of an LCD panel must be the same ata transmission section and a reflection section so that an imageimpression in the transmission mode may match that in the reflectionmode. For this purpose, the voltage-luminance characteristics (V-Tcharacteristics) of the panel in the transmission mode must agree withthose in the reflection mode.

To this end, the present inventor proposes in a prior application(Japanese Patent Application No. 2001-132744) a transflective type LCDwhich has an insulation film with a predetermined film thickness notonly in a reflection region but also in a transmission region so thatthese two regions may have almost the same gap of a liquid crystal layerand also which has polarization adjustment means comprised of apolarization plate and a phase difference plate on both sides of theliquid crystal panel to adjust optical characteristics of these opticalmembers and a twist angle of liquid crystal employed, thus realizinggood display. Prior to describing the present patent application,technologies related to this prior application are described withreference to FIGS. 16 and 17. FIG. 16 is a plan view for showing aconstruction of the active matrix substrate of transflective type LCDrelated to a prior application. And FIG. 17 shows a cross-sectional viewof line c-c′ of FIG. 16.

As shown in FIGS. 16 and 17, the transflective type LCD related to theabove-mentioned prior application comprises an active matrix substrate12, an opposing substrate 16, a liquid crystal layer 17 sandwiched bythese substrates, a back-light source 18 arranged below the activematrix substrate 12, and a plurality of phase difference plates 20 a and20 b as well as polarization plates 19 a and 19 b respectively arrangedon the outer sides of the active matrix substrate 12 and the opposingsubstrate 16.

The active matrix substrate 12 further comprises a gate line 1, a gateelectrode 1 a, a common storage line 4, and an auxiliary capacitanceelectrode 4 a which are formed on a transparent insulation substrate 8,a semiconductor layer, a data line 2, a source/drain electrode, and acapacitance accumulation electrode 2 c which are formed via a gateinsulation film 9, a passivation film 10 covering these, a firstinsulation film 11 a formed as scattered on the passivation film 10, asecond insulation film 11 b which fills a gap between the firstinsulation films to thereby form appropriate irregularities, areflection electrode film 6 formed on the second insulation film 11 b,and a transparent electrode film 5 formed so as to partially overlapwith the reflection electrode film 6 on the second insulation film 11 b.

The first insulation film 11 a is formed in the reflection region asscattered in dot and flat in the transmission region, and depend on thesurface shape of the first insulation film 11 a, the reflectionelectrode film 6 may be shaped irregularly on the second insulation film11 b in the reflection region and that the transparent electrode film 5may be formed flat on the second insulation film 11 b in thetransmission region.

In this configuration, by appropriately setting such opticalcharacteristics of each position as an arrangement angle of the phasedifference plates 20 a and 20 b and a polarization angle of thepolarization plates 19 a and 19 b which plates are all arranged on theouter sides of the both active matrix substrate and the opposingsubstrate, a rubbing angle of these two substrates, a twist angle of theliquid crystal, a gap of the liquid crystal layer 17, etc., it ispossible to remove a residual retardation and compensate for a phasedifference within wide band, thus obtaining a high contrast ratio.

In the above-mentioned prior application, however, when the firstinsulation film 11 a is formed as scattered in dot in the reflectionregion and then heat treated under predetermined conditions to therebyform a desired protrusion shape, the pattern shape of the insulationfilm 11 a before heat treatment is different in the transmission regionand the reflection region, so that after heat treatment the firstinsulation film 11 a becomes thinner in the reflection region andthicker in the transmission region, thus giving rise to a delicatedifference in gap of the liquid crystal layer 17 between these regions.

Further, as shown in FIG. 16, the reflection electrode film 6 is formedin such a manner as to overlap with the transparent electrode film 5 atthe center of each pixel, whereas at a boundary between the adjacentpixels (for example, on the gate line 1 at the upper part in the figure)these two electrodes do not overlap with each other, so that during aphotolithography (PR) step for forming the reflection electrode film 6,a developer soaks into the reflection electrode film 5 through its crackat an edge of the transparent electrode film 5 to trigger electricerosion between Al of the reflection electrode film 6 and ITO of thetransparent electrode film 5, thus possibly eroding the Al or ITOsubstances.

Further, when the opposing electrode 15 is connected with an electrodepad on the side of the active matrix substrate 12 using a conductiveseal, the conductive seal is arranged over a leader wiring, so that toprevent short-circuiting from occurring near a sealing region on theouter side of the liquid crystal, preferably the data line 2 isconnected with a gate layer so that the gate layer may provide a leader(hereinafter called G-D conversion). For this purpose, the G-Dconversion needs to be performed by interconnecting the gate and thedrain metal at their upper layer metal to reduce the contact resistance,thus establishing a process for manufacturing the product with a smallernumber of PR steps while suppressing electric erosion between theabove-mentioned AL and ITO substances.

To this end, the present invention proposes such a transflective typeLCD structure and method for manufacturing the same that can provide thesame gap both in the transmission region and the reflection regions sothat their V-T characteristics may agree with each other and also thatcan suppress electric erosion from occurring between the reflectionelectrode film 6 and the transparent electrode film 5. The followingwill describe the contents in detail with reference to the drawings.

First Embodiment

The following will describe a structure and a principle of thetransflective type LCD related to the first embodiment of the presentinvention with reference to FIGS. 1-5. FIG. 1 is a plan view for showinga configuration of a transflective type LCD related to a firstembodiment of the present invention, and FIG. 2 is a cross-sectionalview in A-A′ line of FIG. 1. FIG. 3 is an illustration for showing apolarization state in each position of the transflective type LCDrelated to the first embodiment of the present invention, and FIG. 4 isa graph for showing a relationship between a twist angle and a gap. FIG.5 are graphs for showing V-T characteristics under predeterminedcondition. Note here that the present embodiment features that anirregular film is formed also in the transmission region as in thereflection region in order to provide the same gap in these regions.

As shown in FIGS. 1 and 2, the transflective type LCD of the presentembodiment comprises the active matrix substrate 12, the opposingsubstrate 16, the liquid crystal layer 17 sandwiched by thesesubstrates, the back-light source 18 arranged below the active matrixsubstrate 12, and the phase difference plates 20 a and 20 b as well asthe polarizing plates 19 a and 19 b respectively arranged on the outersides of the active matrix substrate 12 and the opposing substrate 16.

The active matrix substrate 12 further comprises the gate line 1, thegate electrode 1 a, the common storage line 4, the auxiliary capacitanceelectrode 4 a, the gate insulation film 9, the semiconductor layer, thedata line 2, the source/drain electrode, and the capacitanceaccumulation electrode 2 c which are formed on the transparentinsulation substrate 8 and, on the passivation film 10 covering these,the same shaped irregular film 11 in both the transmission andreflection regions. Further, in the transmission region is formed thetransparent electrode film 5 made of ITO etc., while in the reflectionregion is formed the reflection electrode film 6 made of metal such asAl/Mo. Thus, the reflection region and the transmission regions have theirregular film 11 with the same shape formed therein and so have almostthe same height (specifically with a difference in height of 1 μm orless), thus giving almost the same gap of the liquid crystal layer 17 inthemselves.

The following will describe, with reference to FIGS. 3-5, thearrangement of the polarizing plates and the phase difference plates onthe outer sides of the two substrates and the setting of the twist angleof the liquid crystal and then meanings why the reflection andtransmission regions should have almost the same gap.

[Arrangement of Polarization Plate and λ/4 Plate on the Upper Side]

To provide a normally-white state of the reflection region, that is, astate where it looks white when the liquid crystal is laid with novoltage applied between the opposing substrate and the pixel electrodeand it looks black when the liquid crystal is erected, the phasedifference plate (λ/4 plate) 20 b is arranged between the liquid crystallayer 17 and the polarizing plate 19 b. By then turning the λ/4 plate 20b by 45 degree with respect to the optical axis of the polarizing plate19 b and sandwiching it therebetween, linear-polarized (horizontal)light passing through the polarizing plate 19 b is transformed intoclockwise circular-polarized light. This clockwise circular-polarizedlight arrives at the reflection electrode film 6 as linear-polarizedlight by setting a gap d1 at a predetermined value. The linear-polarizedlight is reflected by the reflection electrode film 6 aslinear-polarized light, which in turn goes out of the liquid crystallayer 17 as clockwise circular-polarized light. This circular-polarizedlight is transformed by the λ/4 plate 20 b into linear-polarized(horizontal) light and then goes out of the polarizing plate 19 b havingthe horizontal optical axis, thus giving white display.

If a voltage is applied on the liquid crystal layer 17, on the otherhand, the liquid crystal is erected. In this state, light injected tothe liquid crystal layer 17 as circular-polarized clockwise arrives atthe reflection electrode film 6 as clockwise circular-polarized light,which in turn is reflected by the reflection electrode film 6 ascounterclockwise circular-polarized light. It is ejected from the liquidcrystal layer 17 as circular-polarized counterclockwise and transformedinto linear-polarized (vertical) light by the λ/4 plate 20 b andabsorbed in it without being ejected therefrom. Thus, display appearsblack.

[Arrangement of λ/4 Plate and Polarizing Plate on the Lower Side]

In the transmission mode, arrangement angles of the optical axes of theλ/4 plate 20 a and the polarizing plate 19 a on the lower side aredetermined so that display may appear black with a voltage applied onthe liquid crystal. The lower side polarizing plate 19 a is arranged ina crossed Nicols manner, that is, as turned by 90 degree with respect tothe upper side polarizing plate 19 b. Further, in order to cancel(compensate for) an influence by the upper side λ/4 plate 20 b, thelower side λ/4 plate 20 a is also arranged as turned by 90 degree. Sincethe liquid crystal is erected when a voltage is applied thereon, thelight is unchanged in polarization state, so that essentially it isoptically equal to a state where the polarizing plates 19 a and 19 b arearranged in the crossed Nicols manner, thus providing black display witha voltage applied. Thus, the arrangement of the optical members of thetransflective liquid crystal panel and the arrangement angles of theiroptical axes are determined.

FIG. 4 shows respective gaps d1 and d2 of the reflection region and thetransmission region which are optimal to maximize of reflectivity andtransmittivity of a white color when the optical members are arranged atthe above-mentioned arrangement angles and the twist angle φ of theliquid crystal is changed over 0-90 degree. FIG. 4 indicates that theoptimal gap of the transmission region is the same as that of thereflection region at a liquid crystal twist angle of 72° and also thatas the liquid crystal twist angle decreases, the optimal gap of thereflection region becomes smaller than that of the transmission region.

Based on these, the present inventor employed nematic liquid crystalwith Δn(refractive index anisotropy)=0.086 and, from FIG. 4, set suchconditions that the gap value d1=d2=2.7 μm and the twist angle is 72degree. The voltage-luminance characteristics (V-T characteristics) ofthe panel in the transmission and reflection modes under theseconditions are shown in FIG. 5A. FIG. 5B shows as a comparison examplethe V-T characteristics under the conventional conditions (twist angleis 0°, d1=1.5 μm, and d2=2.7 μm).

FIG. 5 show that in the configuration of the present embodiment the V-Tcharacteristics of the transmission mode agree well with those of thereflection mode and also the irregular films 11 can be formed in thesame shape throughout the surface of the pixel region to provide almostthe same gap of the liquid crystal as well as almost the same V-Tcharacteristics both in the reflection and transmission regions, thusimproving the display quality.

Although in the present embodiment the irregular films 11 having thesame shape have been formed not only in the reflection region but alsoin the transmission region, the irregular films 11 may not be the samein shape as far as the reflection and the transmission regions havesubstantially the same gap. For example, in the configuration of theabove-mentioned prior application the first insulation film may beformed in two steps so as to be a little thicker in the reflectionregion where it is scattered in dot taking into account a change inshape of thereof, thus providing almost the same total film thicknessincluding the thickness of the second insulation film in these tworegions.

Second Embodiment

The following will describe the transflective type LCD related to thesecond embodiment of the present invention with reference to FIGS. 6 and7. The present embodiment features that to suppress a reaction betweenthe transparent electrode film made of ITO etc. and the reflectionelectrode film made of Al/Mo etc., the positional relationship theseelectrode films is regulated.

The transflective type LCD 12 of the present embodiment comprises theactive matrix substrate 12, the opposing substrate 16, and the liquidcrystal layer 17 sandwiched by these substrates in such a configurationthat on the outer sides of the active matrix substrate 12 and theopposing substrate 16 are respectively arranged the λ/4 plates and thepolarizing plates at the above-mentioned arrangement angle with respectto the optical axis. As the liquid crystal can be employed, for example,nematic liquid crystal NR523LA (Δn=0.086) made by Chisso Corp. with theabove-mentioned settings of the gap value at 2.7 μm and the twist angleat 72°. The opposing substrate is further comprised of a color filterand an opposing electrode for supplying a reference potential.

As shown in FIGS. 6 and 7, on the active matrix substrate 12 arearranged the gate line 1 for supplying a scanning signal, the commonstorage line 4 which gives capacitance, the auxiliary capacitanceelectrode 4 a, the data line 2 for supplying an image signal, the TFT 3connected as a switching element to an intersection of these, and apixel electrodes arranged in matrix at each of the transistors. To thegate electrode 1 a of the TFT 3 is connected the gate line 1 and, to itsdrain electrode is connected the data line 2.

Further, to protect the TFT 3 the passivation film 10 is formed thereon,on which is in turn formed the irregular layer 11 made ofphoto-sensitive acrylic resin which underlies the irregularities of thereflection electrode film 6. On this is further formed the transparentelectrode film 5 composed of a transparent conductive film made of ITOetc., on which is formed the reflection electrode film 6 made ofhigh-reflectivity metal such as Al.

Note here that, as mentioned above, in the prior application of thepresent inventor (see FIGS. 16 and 17), the transparent electrode film 5and the reflection electrode film 6 are separated from each other in aregion between the adjacent pixels, in which region of the transparentelectrode film 5 is eroded at its edge when the reflection electrodefilm 6 is patterned, thus giving a defective pixel in some cases.

To suppress this electric erosion reaction between the reflectionelectrode film 6 and the transparent electrode film 5, the presentpatent application employs a variety of countermeasures. One is toadjust the positional relationship between the reflection electrode film6 and the transparent electrode film 5. Specifically, as shown in FIG.6, a window portion which provides a transmission region is formed inthe reflection electrode film 6 in each of the pixels to thereby set apositional relationship between the reflection electrode film 6 and thetransparent electrode film 5 so that these two films may overlap witheach other around the overall periphery of this window portion.

That is, one cause of erosion is considered as follows: at the edge ofthe transparent electrode film 5 the reflection electrode film 6deposited thereon has poor coverage due to a crack etc., through which adeveloper soaks into the poor coverage portion when forming a resistpattern for reflection electrode film 6. To guard against this, apredetermined overlap region is provided between the transparentelectrode film 5 and the reflection electrode film 6 to cover the edgeof the transparent electrode film 5 with a resist pattern in order toprevent the developer from coming in direct contact therewith, thusavoiding erosion of the transparent electrode film 5. Note here that anextent of the overlapping should be enough only to cover the poorcoverage portion, which is specifically 2 μm or so as confirmedexperimentally by the present inventor.

Furthermore, by forming the reflection electrode film 6 in such a mannerthat it may overlap with the transparent electrode film 5 around itsoverall periphery, an area in which these two films 5 and 6 come incontact with each other can be increased advantageously. That is, in acase of the reflection region is formed on the side of the TFT 3, thesource electrode of the TFT 3 and the reflection electrode film 6 can beinterconnected via a contact hole 7 formed through the irregular layer11 and the passivation film 10 to connect the transparent electrode film5 to the reflection electrode film 6 in order to thereby interconnectthe source electrode and the transparent electrode film 5, so thatcontact resistance between the transparent electrode film 5 and thereflection electrode film 6 can be decreased by forming these two filmsin such a manner that they may overlap with each other around theoverall periphery. Moreover, by connecting the transparent electrodefilm 5 around its overall periphery, such an effect can be expected asto provide a uniform potential everywhere on the transparent electrodefilm 5, thus accurately controlling a voltage applied on the liquidcrystal.

Although the present embodiment has been described with reference to aconfiguration in which one rectangular window portion is formed in thereflection electrode film 6, the present invention is not limitedthereto; for example, the window portion may be polygonal, circular,elliptical, or of any other arbitrary shape and be provided more thanone in each pixel, as far as the reflection electrode film 6 overlapswith the transparent electrode film 5 around its overall periphery.Furthermore, although in FIG. 7 the irregular film 11 is shapedirregular in the reflection region and flat in the transmission region,it may be formed irregular in both of the regions 5 and 6 as shown inFIG. 2 and their surfaces may be of an arbitrary shape.

Third Embodiment

The following will describe a transflective type LCD manufacturingmethod related to the third embodiment of the present invention withreference to FIGS. 8-10. Here, FIGS. 8-10 are drawings for explainingproblems in production process of the active matrix substrate. Note herethat the present embodiment features that the electric erosion reactionis suppressed from occurring between the transparent electrode film andthe reflection electrode film.

In the above-mentioned second embodiment, as shown in FIG. 8B (expandedview of a defective portion of FIG. 8A), a problem that a developersoaks into the reflection electrode film 6 through its crack at the edgeof the transparent electrode film 5 during a PR process for processingof the reflection electrode film 6 is solved by adjusting the planarpositional relationship between the reflection electrode film 6 and thetransparent electrode film 5. To suppress electric erosion fromoccurring between the reflection electrode film 6 and the transparentelectrode film 5 more securely, it is necessary to improve adhesivenessof the transparent electrode film 5 to improve the coverage of thereflection electrode film 6 in an area of the edge of the transparentelectrode film 5. In view of this, the present embodiment features amethod of adjusting the thickness of the reflection electrode andoptimizing a cleaning step before the transparent electrode film 5 isformed to thereby suppress electric erosion from occurring between thereflection electrode film 6 and the transparent electrode film 5. Thefollowing will describe a mechanism of and how to suppress electricerosion from occurring between the ITO substrate of the transparentelectrode film 5 and the Al substrate of the reflection electrode film6.

(1) Mechanism of ITO-Al Electric Erosion

Combination is very bad between an Al-based material, which is highlyreactive and easily reacts with oxygen to form an oxide film (Al₂O₃),and ITO, which is an oxide conductor. Particularly when forming apositive resist pattern on a layered film consisting of an upper layermade of Al and a lower layer made of ITO, so-called electric erosionoccurs to erode (oxidize) Al and dissolve (reduce) ITO, thus giving poorcontact between Al and ITO (see FIG. 8B). This electric erosion reactionis considered to occur by the following mechanism.

-   -   1. Such an Al portion as to have many lattice defects or        impurities dissolves as a local anode, thus giving rise to a pin        hole;    -   2. Through thus formed pin hole, a developer comes in contact        with the underlying ITO;    -   3. A potential difference between an oxidizing potential of Al        in the developer and a reducing potential of ITO triggers the        reaction, thus promoting oxidization of Al and reduction of ITO        respectively indicated by the following reaction formulae:        Al+4OH⁻¹→H₂AlO₃+H₂O+3e  (1)        In₂O₃+3H₂O+6e→2In+6OH⁻  (2)        (2) Film Thickness of Mo as Barrier Metal

The above-mentioned phenomenon of electric erosion accurring between Aland ITO substance can be suppressed to some extent by inserting Mo et.as the barrier metal between these substances. However, the Al and Mosubstances deposited by suttering are generally columnar crystal, sothat a developer soaks into them through a gap between the columns totouch off electric erosion if Al and Mo do not have sufficient filmthickness. As such, the present inventor investigated an extent to whichthe electric erosion reaction occurs when the film thickness of Al andMo formed on the ITO are changed respectively. A correlation betweenthese is given in a table below. In the table, X indicates significantoccurrence of electric erosion, Δ indicated partial occurrence, ◯indicated almost no occurrence, and ⊙ indicates no occurrence.

TABLE 1 Mo film thickness Al film thickness Electric erosion  50 nm (500A)  50 nm X 100 nm X 200 nm X 100 nm  50 nm X 100 nm Δ 200 nm ◯ 200 nm 50 nm X 100 nm Δ 200 nm ◯ 100 nm twice  50 nm X 100 nm Δ 200 nm ⊚ 100nm twice ⊚

Table 1 indicates that to suppress electric erosion from occurring, itis necessary to form both Mo and Al films to a film thickness of 100 nm(1000 Å) or more, preferably 200 nm or more. Furthermore, it was foundthat when forming the Mo and Al films, rather than forming them, forexample, to a thickness of 200 nm at a time, preferably they are formedto a thickness of 100 nm, then washed with an alkali solution once, andthen formed to another thickness of 200 nm, in order to improve theirperformance as a barrier. Although not clear, the reason may be that thesurface of Mo dissolves by alkali washing and is reduced incolumnar-ness, so that when once exposed to the air or the washingsolution, the Mo surface has a thin film formed thereon and, when formedsecond time, is changed in crystallinity.

(3) Adhesiveness of ITO on Irregular (Organic) Film

Paragraphs (1) and (2) have described how to improve the performance ofbarrier metal. No matter how the barrier metal performance is improved,however, unless the transparent electrode film 5 made of ITO ispatterned with good adhesiveness on the underlying irregular film 11,the developer soaks through a gap into the reflection electrode film 6to give rise to electric erosion as shown in FIG. 8C.

Generally, prior to sputtering of the ITO, ultra-violet (UV) ray isapplied to decomposes an organic substance such as oil and then purewater or a weak alkali solution is used for washing, a step of whichwashing was experimentally confirmed by the present inventor to have aninfluence on the adhesiveness of the ITO. Table 2 below shows acorrelation between electric erosion and an application quantity of UVray prior to ITO sputtering. In the experiment, UV ray with a wavelengthof 300 nm was applied with a quantity of 0 mJ through 1 J.

TABLE 2 UV application quantity Electric Erosion  0 mJ ◯ 100 mJ Δ 250 mJX 500 mJ X  1 J X

Table 2 indicates that electric reaction is liable to occur at aquantity of 100 mJ or more of UV ray application. A mechanism for thatis considered as follows: a polymer network on the surface of theirregular film 11 made of an organic substance such as acrylic isdestroyed by UV ray and, when an ITO film is formed thereon andpatterned by photolithography (PR), the surface of the irregular film 11on which the polymer network is destroyed dissolves in an etch-offsolution during an etch-off step, thus causing the edge of the ITO tolift.

When the ITO is thus peeled, a lift cannot completely be covered bybarrier metal, if provided to the reflection electrode film 6.Especially in such a configuration of FIG. 8 that the reflectionelectrode film 6 is not overlapped at the edge of the ITO, a resistpattern 21 used for processing of the reflection electrode film does notcover the edge of the ITO, so that a developer soaks through a gapbetween the electrodes during a developing step, thus giving rise toelectric erosion as confirmed by the experiment.

In contrast, in such a configuration of the present embodiment that theedge of the ITO is totally covered by the reflection electrode film 6 asshown in FIG. 9, the resist pattern used to etch the reflectionelectrode film 6 also covers the edge of the ITO to thereby block thedeveloper, thus preventing it from disadvantageously soaking throughduring the developing step.

Thus, at the washing step prior to ITO sputtering, by limiting theapplication quantity of UV ray down to 100 mJ or less or even byeliminating the UV ray application step and also by setting the filmthickness of both the barrier metal and Al films of the reflectionelectrode film 6 at 100 nm or more, preferably 200 nm or more, it ispossible to efficiently suppress electric erosion between the ITO and Alsubstances, thus preventing the conventional dissolving of ITO and Al(see a microscopic picture of FIG. 10).

Although the above-mentioned embodiments have employed Mo as the barriermetal of the reflection electrode film 6, the barrier metal is notlimited to it but may be Cr, Ti, W, etc. instead. Also, although thefilm thickness of the Al and Mo substances have been set at 100 nm ormore, preferably 200 nm or more, the optimal film thickness may beadjusted appropriately corresponding to the film formation conditionsincluding sputtering etc.

Fourth Embodiment

The following will describe the transflective LCD manufacturing methodaccording to the fourth embodiment of the present invention withreference to FIGS. 11-13. FIG. 11 and FIG. 12 are cross-sectional flowdiagrams for showing a transflective type LCD manufacturing methodrelated to a fourth embodiment of the present invention, and FIG. 13 arethe cross-sectional flow diagrams for showing the method for forming theirregularity film. The present embodiment gives a specific manufacturingmethod which enables G-D conversion to prevent short-circuiting of aleader wiring owing to a conductive seal in addition to taking intoaccount the conditions described with the above-mentioned embodiments.The method is described with reference to these figures.

First, as shown in FIG. 11A, metal such as Cr is deposited on thetransparent insulation substrate 8 made of glass and patterned withpublicly known photolithography and etching technologies to form thegate line, the gate electrode 1 a, the common storage line, and theauxiliary capacitance electrode 4 a. Then, a semiconductor layer made ofa-Si etc. is deposited via the gate insulation layer film 9 made ofSiO₂, SiNx, SiON, etc. and patterned into islands, on which metal suchas Cr is in turn deposited and patterned to form the data line, thedrain electrode 2 a, the source electrode 2 b, and the capacitanceaccumulation electrode 2 c.

Next, as shown in FIG. 11B, the passivation film 10 made of SiNx etc.for protecting the TFT 3 is formed with plasma-enhanced CVD, after whichthe gate insulation film 9 and the passivation film 10 at the G-Dconversion portion and the terminal portions are partially removed toform a contact hole. Then, a conductive material made of ITO, Al, etc.is deposited to form a terminal electrode 23 and a G-D conversionelectrode 22 for interconnecting the drain and gate layers at the G-Dconversion portion.

Next, as shown in FIG. 11C, to form irregularities of the reflectionelectrode film 6 on the passivation film 10 to improve visibility ofreflection light, an irregular film 11 is formed. This irregular film 11is formed by applying photo-sensitive acrylic resin, for example, PC403,415G, 405G, etc. made by JSR Co. using spin coating. Furthermore, thephoto-sensitive acrylic resin is under-exposed with a little smallerquantity of exposure in an expected recess region of the irregularities,not exposed on an expected protrusion region of them, and exposed with asufficient quantity of exposure in the expected contact hole region.

To enable such exposure, a half-tone (gray tone) mask can be used onwhich a reflection film is formed at a portion which corresponds to theexpected protrusion region, a transmission mask is formed at a portionwhich corresponds to the expected contact hole region, and atransflective film is formed at a portion which corresponds to theexpected recess region, thus requiring exposing only once to form theirregularities. In this case, even an ordinary mask comprised of onlyreflection/transmission films can be used to form the irregularities byexposing the expected contact hole and recess regions separately withdifferent exposure quantities.

Next, an alkali developer is used to form the irregularities byutilizing a difference in dissolving rate in an alkali solution of theexpected recess, protrusion, and contact hole regions. Note here that bythe present invention, in order to form the irregular film 11 even inthe transmission region, the acrylic film is decolorized by exposing theoverall surface to suppress transmission light from being attenuated bythe irregular mask 11. Then, the surface is cured, for example, at 220°C. for one hour to form the irregular film 11 having a desired shape.

Although as mentioned above this irregular mask 11 may be formed byforming one layer of photo-sensitive acrylic resin and then changing anexposure quantity partially, it may be formed using a plurality ofphoto-sensitive acrylic resin. For example, as shown in FIG. 13A,desired irregularities can be formed by forming first layer ofphoto-sensitive acrylic resin in a shape of islands, then heat treatingit to form the first insulation film 11 a, then applying thereon thesecond insulation film 11 b made of photo-sensitive acrylic resin havinga predetermined value of viscosity, and then filling the gap between theislands of the first insulation film 11 a.

Next, as shown in FIG. 12A, a transparent conductive film made of ITOetc. is formed by sputtering, in which step preferably a UV applicationquantity is 100 mJ or less as described with the third embodiment. Then,thus formed ITO is patterned into a predetermined shape to form thetransparent electrode film 5 in the transmission region.

Next, as shown in FIG. 12B, Mo is used as barrier metal to suppresselectric erosion between ITO and Al of the reflection electrode, to formMo and Al films which act as the barrier metal and the reflection metalrespectively. In this case, as described with the third embodiment, theMo and Al films are formed to a thickness of 100 nm or more, preferably200 nm or more and also in two steps to suppress the columnar crystalfrom growing by sputtering. Then, the Al/Mo films are collectivelywet-etched to pattern the reflection electrode film 6. In this case, asdescribed with the second embodiment, to suppress the ITO edge frombeing etched off by the developer, preferably the positionalrelationship of the Al/Mo films is set so that they may overlap witheach other around the overall periphery of the ITO.

Thus, this method of manufacturing the active matrix substrate makes itpossible to obtain a transflective type LCD in which the peeling of thetransparent electrode film 5 and the electric erosion between thetransparent electrode film 5 and the reflection electrode film 6 can besuppressed to prevent occurrence of a defective pixel and also G-Dconversion is conducted around the outer periphery of the liquid crystalpanel.

Fifth Embodiment

The following will describe the transflective type LCD and method formanufacturing the same related to the fifth embodiment of the presentinvention with reference to FIGS. 14 and 15. FIGS. 14 and 15 arecross-sectional flow diagrams for showing the transflective type LCDmanufacturing method related to a fifth embodiment of the presentinvention. The present embodiment has simplified the manufacturingmethod as compared to the fourth embodiment. The method is describedbelow with reference to these figures.

First, as by the above-mentioned fourth embodiment, as shown in FIG.14A, on a transparent insulation substrate made of glass aresequentially formed the gate line, the gate electrode 1 a, the commonstorage line, and the auxiliary capacitance electrode 4 a, on which aresequentially formed the gate insulation film 9, the semiconductor layer,the data line, the drain electrode, the source electrode, and thecapacitance accumulation electrode 2 c. Then, after the passivation film10 which protects the TFT 3 is formed, the gate insulation film 9 andthe passivation film 10 at the G-D conversion portion and the terminalportion are etched off to form a contact hole.

In contrast to the fourth embodiment in which after the contact hole isformed, the conductive materials such as ITO, Al, etc. for G-Dconversion are formed as a film and patterned, the present embodimentsimplifies the manufacturing steps by using the transparent electrodefilm 5 and the reflection electrode film 6 which are formed in thesubsequent steps, to interconnect the drain and gate layers of the G-Dconversion portion and form the terminal electrode.

Next, as shown in FIG. 14B, the irregular film 11 is formed to formirregularities of the reflection electrode film 6. For example, thephoto-sensitive acrylic resin is under-exposed with a little smallerquantity of exposure in an expected recess region of the irregularities,not exposed on an expected protrusion region of them, and exposed with asufficient quantity of exposure in the expected contact hole 7 region.Then, an alkali developer is used to form the irregularities byutilizing a difference in dissolving rate in an alkali solution of theseregions. Then, the surface is thoroughly exposed to decolorize theacrylic film and cured, for example, at 220° C. for one hour to form theirregular film 11.

Next, after the surface is washed under the conditions of a UVapplication quantity being 100 mJ or less, as shown in FIG. 14C, atransparent conductive film made of ITO etc. is formed by sputtering andpatterned to form the transparent electrode film 5 in the transmissionregion. At the same time, ITO is formed also at the terminal portion toform the terminal electrode 23.

Next, as shown in FIG. 14D, a Mo film with a film thickness of 100 nm ormore, preferably 200 nm or more, and an Al film with a film thickness of100 nm or more, preferably 200 nm or more, are formed consecutively.Then, the Al/Mo films are wet-etched collectively to pattern thereflection electrode film 6. At the same time, Al/Mo films are formedalso at the G-D conversion portion to interconnect its drain and sourcelayers.

Thus, by the above-mentioned manufacturing method, the layers of the G-Dconversion portion are interconnected using the reflection electrodefilm 6 and the terminal electrode 23 is formed using the transparentelectrode film 5, so that it is possible to eliminate the step offorming and patterning the ITO film for G-D conversion etc. in contrastto the fourth embodiment.

Although the present embodiment deposits the reflection electrode film 6in the contact hole 7 to connect it with the source electrode and thenwith the transparent electrode film 5 at the overlapping portionthereof, the contact may not be enough only with the reflectionelectrode film 6 in some cases because the irregular film 11 in whichthe contact hole 7 is formed has a large step. To secure the contact,the following manufacturing method may be employed.

First, as shown in FIG. 15A, on the transparent insulation substrate 8are sequentially formed the gate line, the gate electrode 1 a, theauxiliary capacitance electrode 4 a, the gate insulation film 9, thesemiconductor layer, the data line, the drain electrode 2 a, the sourceelectrode 2 b, and the capacitance accumulation electrode 2 c. Then,after the passivation film 10 which protects the TFT 3 is formed, thegate insulation film 9 and the passivation film 10 at the G-D conversionportion and the terminal portion are etched off to form the contacthole.

Next, as shown in FIG. 15B, the irregular film 11 is formed to formirregularities of a reflection plate. For example, the photo-sensitiveacrylic resin is under-exposed with a little smaller quantity ofexposure in an expected recess region of the irregularities, not exposedon an expected protrusion region of them, and exposed with a sufficientquantity of exposure in the expected contact hole region and then, analkali developer is used to form the irregularities by utilizing adifference in dissolving rate in an alkali solution of these regions.Then, the surface is thoroughly exposed to decolorize the acrylic filmand cured, for example, at 220° C. for one hour to form the irregularfilm 11.

Next, after the surface is washed under the conditions of a UVapplication quantity being 100 mJ or less, as shown in FIG. 15C, atransparent conductive film made of ITO etc. is formed by sputtering andpatterned to form the transparent electrode film 5 in the transmissionregion and the terminal electrode 23 as well. At the same time, ITO isdeposited also in the contact hole 7 to fill with it completely orpartially.

Next, as shown in FIG. 15D, the Mo film and the reflecting Al metal filmeach having a film thickness of 100 nm or more, preferably 200 nm ormore, are formed consecutively. Then, the Al/Mo films are wet-etchedcollectively to pattern the reflection electrode film 6. At the sametime, the reflection electrode film 6 is formed also at the G-Dconversion portion to interconnect its drain and source layers. In thiscase, the transparent electrode film 5 is already deposited in thecontact hole 7, so that even if the contact hole 7 has a large aspectratio, secure contact can be obtained between the source electrode andthe reflection electrode film 6.

Thus, by the above-mentioned manufacturing method, the contact holeprovided on the source electrode 2 c of the TFT3 continues electricallyto the reflection electrode film 6 and the transparent electrode film 5in this order, so that contact can be secured even if the irregular film11 is thick and the contact hole 7 has a large aspect ratio.

As mentioned above, the transflective type LCD and method formanufacturing the same according to the present invention has thefollowing effects.

As the first effect of the present invention, for example, the V-Tcharacteristics of the transmission mode can agree with those of thereflection mode to thereby improve a display quality.

The reason is that the irregular film is formed almost in the same shapeeverywhere on the surface of the pixel region to thereby provide almostthe same gap in both the reflection region and the transmission regionmode.

As the second effect, it is possible to suppress electric erosion fromoccurring between the transparent electrode film made of ITO etc. andthe reflection electrode film made of Al etc. to thereby preventoccurrence of abnormal display.

The reason is that the reflection electrode film is formed inconfiguration all around the edge of the ITO film to cover the edge witha resist for processing the reflection electrode film when the resist isformed, thus preventing the developer from coming in contact therewith.

Furthermore, by using Mo as the barrier metal of the reflectionelectrode film and setting the film thickness of the Mo and Al films ata predetermined value or more and also limiting the UV applicationquantity at the washing step prior to formation of the ITO film down toa predetermined value or less, the close contact-ness of the ITO film isimproved to prevent the etchant or the developer from soaking through.

1. A method for manufacturing a transflective type LCD having a firstsubstrate provided thereon with a plurality of scanning lines and aplurality of signal lines which are substantially perpendicular to eachother and a switching element arranged near each of intersectionsbetween said scanning lines and said signal lines, forming a reflectionregion having a reflection electrode film and a transmission regionhaving a transparent electrode film in a pixel region surrounded by saidscanning lines and said signal lines, a liquid crystal being sandwichedat a gap between said first substrate and a second substrate which isarranged opposite to said first substrate, the method comprising:forming an organic film below said reflection electrode film and saidtransparent electrode film to substantially the same film thickness,said organic film comprising an irregular surface having irregularitiesand formed below said reflection electrode film and said transparentelectrode film, and said forming said organic film comprising: forming ahalf-tone mask having a transmission portion, a shielding portion and atransflective portion in said pixel region; and in said pixel region,using said transflective portion of said mask to form saidirregularities in a portion of said organic film, and using saidtransmission portion of said mask to form a contact hole in anotherportion of said organic film; forming said transparent electrode film onsaid irregular surface; and forming said reflection electrode film onsaid transparent electrode film, said forming said reflection electrodefilm comprising: forming a barrier metal film of the reflectionelectrode film on the transparent electrode film and a reflection metalfilm of the reflection electrode film on the barrier metal film, thebarrier metal film and reflection metal film each comprising a thicknessof 100 nm or more; forming a resist pattern on said reflection electrodefilm, said resist pattern overlapping said reflection electrode film andan edge portion of said transparent electrode film, said forming saidresist pattern comprising developing said resist pattern by using adeveloper, said overlapping resist pattern inhibiting said developerfrom contacting said edge portion of said transparent electrode film;and etching said reflection electrode film using said resist patternsuch that said reflection electrode film overlaps said edge portion ofsaid transparent electrode film by at least 2 μm around an overallperiphery of said transparent electrode film.
 2. The method according toclaim 1, wherein said reflection electrode film includes a two-layerconstruction comprising a barrier metal film and a reflection metalfilm, each of which is formed to a film thickness of about 200 nm ormore.
 3. The method according to claim 1, wherein when at least one ofsaid barrier metal film and said reflection metal film is formed, themetal film is once formed to a predetermined film thickness, then washedby an alkali solution, and then formed again to a desired filmthickness.
 4. The method according to claim 3, wherein at the washing byuse of UV ray prior to formation of said transparent electrode film, anapplication quantity of the UV ray is limited down to a value less than100 mJ.
 5. The method according to claim 1, wherein said barrier metalfilm comprises Mo and said reflection metal film comprises Al.
 6. Themethod according to claim 1, wherein said contact hole in said organicfilm is formed below said reflection electrode film.
 7. The methodaccording to claim 1, further comprising: forming a metal layer on saidorganic film, a portion of said metal layer forming said reflectionelectrode film and a portion of said metal layer forming a contact insaid contact hole for electrically connecting said reflection electrodefilm with a capacitance accumulation electrode.
 8. The method accordingto claim 1, wherein said forming said half-tone mask comprises forming atransflective portion of said mask in said transmission region.
 9. Themethod according to claim 1, wherein said using said transflectiveportion of said mask comprises using said transflective portion of saidmask to form irregularities in said transmission region.
 10. The methodaccording to claim 1, wherein said resist pattern overlaps saidreflection electrode film and said transparent electrode film around anentire periphery of said transparent electrode film.
 11. The methodaccording to claim 1, wherein said etching said reflection electrodefilm comprises using said resist pattern to suppress an etching off ofan edge of said transparent electrode film.
 12. The method according toclaim 1, wherein said transparent electrode film comprises an irregularsurface.
 13. The method according to claim 1, further comprising:forming a passivation film in the pixel region, the organic film beingformed on the passivation film; and using the transmission portion ofthe mask to form a contact hole in the passivation film which is alignedwith the contact hole in the organic film.
 14. The method according toclaim 13, further comprising: forming a capacitance accumulationelectrode on the first substrate, the passivation film being formed onthe capacitance accumulation electrode, wherein forming the reflectionelectrode film comprises forming a contact between the reflectionelectrode film and the capacitance accumulation electrode by filling thecontact hole in the organic film and the contact hole in the passivationfilm.
 15. The method according to claim 1, wherein the reflectionelectrode film overlaps said edge portion of said transparent electrodefilm such that the reflection electrode film is configured to apply auniform potential over an entire area of the transparent electrode film.16. A method of manufacturing a transflective type liquid crystaldisplay (LCD), the method comprising: providing a transparent substratehaving a passivation film formed thereon; forming an irregular film onsaid passivation film, said irregular film comprising irregularities ina reflection region and a transmission region of a pixel region, saidforming said irregular film comprising: depositing a photosensitive filmon said passivation film; forming a half-tone mask on saidphotosensitive film in said pixel region of said LCD; and in said pixelregion, using a transflective portion of said mask to form an irregularsurface including irregularities in a portion of said photosensitivefilm and using a transmission portion of said mask to form a contacthole in another portion of said photosensitive film; forming atransparent electrode film on said irregular surface; and forming areflection electrode film on said transparent electrode film, saidforming said reflection electrode film comprising: forming a barriermetal film of the reflection electrode film on the transparent electrodefilm and a reflection metal film of the reflection electrode film on thebarrier metal film, the barrier metal film and reflection metal filmeach comprising a thickness of 100 nm or more; forming a resist patternon said reflection electrode film, said resist pattern overlapping saidreflection electrode film and an edge portion of said transparentelectrode film, said forming said resist pattern comprising developingsaid resist pattern by using a developer, said overlapping resistpattern inhibiting said developer from contacting said edge portion ofsaid transparent electrode film; and etching said reflection electrodefilm using said resist pattern such that said reflection electrode filmoverlaps said edge portion of said transparent electrode film by atleast 2 μm around an overall periphery of said transparent electrodefilm.
 17. The method according to claim 16, wherein said providing saidtransparent substrate comprises: forming a metal layer on saidtransparent substrate to form an auxiliary capacitance electrode;forming a gate insulation layer on said transparent substrate; forming apatterned semiconductor layer on said gate insulation layer; forming apatterned metal layer on said patterned semiconductor layer to form adrain electrode, source electrode and capacitance accumulationelectrode; and forming said passivation film on said drain electrode,source electrode and capacitance accumulation electrode, saidpassivation film comprising a contact hole formed using said mask whichis used to form said contact hole in said photosensitive film.
 18. Themethod according to claim 17, wherein said forming said reflectionelectrode film comprises forming a contact in said contact hole of saidpassivation film, said contact electrically connecting said reflectionelectrode film with said capacitance accumulation electrode.
 19. Themethod according to claim 16, wherein said using said mask comprisesexposing said photosensitive film to different quantities of exposure.20. The method according to claim 16, wherein said mask comprises ahalf-tone mask including a reflection film in an expected protrusionregion of said irregular film, a transmission film in an expectedcontact hole region of said irregular film, and a transflective film inan expected recess region of said irregular film.
 21. The methodaccording to claim 20, wherein said forming said irregular film furthercomprises: dissolving exposed portions of said photosensitive film usingan alkali developer comprising an alkali solution, such that dissolvingrates are different in said expected protrusion region, said expectedcontact hole region and said expected recess region; and curing saidphotosensitive film.
 22. The method according to claim 16, wherein saidphotosensitive film comprises a photosensitive acrylic resin film.
 23. Amethod of forming a transflective type liquid crystal display (LCD),said method comprising: forming an irregular film, comprising: providinga transparent substrate having a passivation film formed thereon;depositing a photosensitive film on said passivation film; forming ahalf-tone mask on said photosensitive film in a pixel region of saidLCD; in said pixel region, using a transflective portion of said mask toform an irregular surface including irregularities in a portion of saidphotosensitive film, and using a transmission portion of said mask toform a contact hole in another portion of said photosensitive film, saidirregularities of said irregular film being formed in a reflectionregion and a transmission region of said pixel region; forming atransparent electrode film on said irregular surface; and forming areflection electrode film on said transparent electrode film, saidforming said reflection electrode film comprising: forming a barriermetal film of the reflection electrode film on the transparent electrodefilm and a reflection metal film of the reflection electrode film on thebarrier metal film, the barrier metal film and reflection metal filmeach comprising a thickness of 100 nm or more; forming a resist patternon said reflection electrode film, said resist pattern overlapping saidreflection electrode film and an edge portion of said transparentelectrode film, said forming said resist pattern comprising developingsaid resist pattern by using a developer, said overlapping resistpattern inhibiting said developer from contacting said edge portion ofsaid transparent electrode film; and etching said reflection electrodefilm such that said reflection electrode film overlaps said edge portionof said transparent electrode film by at least 2 μm around an overallperiphery of said transparent electrode film.